title: Halide ions effects on surface excess of long chain ionic liquids water solutions.
abstract: The interfacial structure and composition of water solutions with alkylimidazolium ionic liquids varying in their halide anions ([C12mim][X], X = Cl and I) were investigated by X-ray near-total-reflection fluorescence spectroscopy and X-ray reflectivity measurements. We demonstrate that X-ray fluorescence and reflectivity techniques provide a more direct measurement of surface adsorption. Furthermore, we show that for [C12mim][Cl] and [C12mim][I] solutions with mixed inorganic salts (NaI, NaCl), I(-) ions replace Cl(-) above the critical micelle concentration (CMC) of [C12mim][Cl] at much lower concentrations of NaI, whereas NaCl concentrations a hundred times higher than the CMC of [C12mim][I] only partially replace the I(-) at the interface. Our surface-sensitive X-ray diffraction and spectroscopy provide two independent tools to directly determine the surface adsorption of ionic surfactants and the interfacial composition of the surface films.
authors.affiliation: Ames Laboratory and Department of Physics and Astronomy, Iowa State University , Ames, Iowa 50011, United States.
authors.forename: Wenjie
authors.initials: W
authors.lastname: Wang
authors.forename: Woongmo
authors.initials: W
authors.lastname: Sung
authors.forename: Mingqi
authors.initials: M
authors.lastname: Ao
authors.forename: Nathaniel A
authors.initials: NA
authors.lastname: Anderson
authors.forename: David
authors.initials: D
authors.lastname: Vaknin
authors.forename: Doseok
authors.initials: D
authors.lastname: Kim
mesh_terms: D007093:Imidazoles / Q000737:chemistry; D052578:Ionic Liquids / Q000737:chemistry*; D007477:Ions / Q000737:chemistry; D008823:Micelles; D012965:Sodium Chloride / Q000737:chemistry*; D012974:Sodium Iodide / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry; D013500:Surface Tension; D014867:Water / Q000737:chemistry*
chemical_list: C521425:1-dodecyl-3-methylimidazolium; D007093:Imidazoles; D052578:Ionic Liquids; D007477:Ions; D008823:Micelles; D012996:Solutions; D014867:Water; D012965:Sodium Chloride; D012974:Sodium Iodide